I. Field of the Invention
The invention relates to a delivery system for agriculturally active chemicals. More particularly, the invention relates to an emulsifiable concentrate of difficult to dissolve agricultural chemicals making use of biodegradable solvents.
II. Description of the Prior Art
Agricultural chemicals are most preferably applied in the form of aqueous emulsions, solutions, or suspensions. Occasionally, they may also be applied in the form of a dust wherein the active ingredient is adsorbed onto or mixed with a finely divided inert carrier material, such as, china clay, or the like. With such powdered or dust compositions, drift due to wind is a problem and consequently, liquid formulations are preferred.
One of the problems with such liquid formulations is the fact that chemicals having agricultural activity often exhibit extreme insolubility in water. This results in their having to be dissolved either in organic solvents or utilized in the form of emulsions or suspensions. With respect to the use of organic solvents, these are generally disadvantageous from an environmental and cost viewpoint. Particularly, such organic chemicals may exhibit toxicity or side-effects which may be adverse to the effect of the agricultural chemical itself or to the subsequent fruit or vegetable produced in the particular agricultural use. This toxicity may also be disadvantageous with respect to handling.
When attempts are made to provide emulsified or suspension formulations, difficulties are encountered with respect to providing a desirably high concentration of the agriculturally active ingredient. Thus, when such agriculturally active chemicals are formulated into an emulsion, it is difficult to maintain the emulsified state. This makes it difficult to maintain a uniform formulation, particularly, when the formulation is diluted with water for application to the plants.
Typically, for example, the agriculturally active ingredient is mixed with one or more of a variety of conventional solvents and an emulsifying agent to form a concentrate. This concentrate may be an emulsion, suspension, or solution. The concentrate is then stored until it is transported to the site of use or may simply be transported and stored at the site of use. In any event, the concentrate normally will undergo some period of storage until it is ready for use. Understandably, it is most desirable to be able to transport the agriculturally active ingredient at the highest concentration possible so as to minimize the volume of material which need be transported. By the same token, however, at the use site, it is normally not feasible to admix ingredients together or to process them other than to dilute the concentrate with water. Accordingly, it is important that the concentrate emulsify easily, i.e., exhibit good "bloom", upon the addition of water. In addition, at the use site, it is often necessary to store the diluted concentrate for extended time periods until the actual application to the plants. Consequently, it is important that the diluted form of the concentrate exhibit good stability with respect to the uniformity of the emulsion and to avoid precipitation of the active ingredients. If non-uniformity or precipitation occurs in the diluted form, then non-uniformity will result in the application of the diluted formulation to the plants.
Substantial progress in providing emulsifiable concentrates which avoid the problems of the prior art are disclosed in U.S. patent applications Ser. No. 448,707, filed Dec. 11, 1989, Ser. No. 505,030, filed Apr. 5, 1990, and Ser. No. 546,014, filed Jun. 28, 1990, the contents of all of which are incorporated herein by reference. The emulsifiable concentrates of these disclosures all require the presence of a hydrophobic solvent having the following Hansens' solubility parameters:
Dispersive component from about 56 to 75%; PA1 Polar component from about 8 to 24%; and PA1 H-bonding component of from about 10 to 30%.
This second component should also have surfactant properties and act as a non-ionic surfactant with an HLB value ranging from about 2 to 8. Examples of this solvent or component include alkylpyrrolidones having an alkyl portion containing from 6 to 14 carbon atoms, e.g., octylpyrrolidone, dodecylpyrrolidone, or N-(2'-ethylhexylpyrrolidone), alkyl gamma-butyrolactones, alkyl cyclic carbonates and combinations thereof, wherein the alkyl chains contain from 6 to 14 carbon atoms. The alkyl portion may be distributed at one or more sites on the ring so long as one portion contains at least 6 carbon atoms and the total number of alkyl carbon atoms does not exceed 14. For each of the above examples, the 6 to 14 carbon alkyl portions may be straight, branched, or cyclic, with straight chains being preferred. The preferred component or hydrophobic solvent is indicated as being long chain alkyl, and particularly those selected from pyrrolidones having the formula ##STR2## wherein R.sub.2 is hydrogen or alkyl having from 6 to 14 carbon atoms and R.sub.3 is alkyl having from 6 to 14 carbon atoms with the proviso that at least one of R.sub.2 or R.sub.3 must contain at least 6 carbon atoms and the sum of the carbon atoms in R.sub.2 and R.sub.3 cannot exceed 14.